The proliferation of media players, cellular telephones and numerous other electronic devices has grown immensely in recent years. Many of the wide varieties of such devices have given rise to some interesting manufacturing developments. For example, many electronic devices have housings that are made from several different parts, as well as complex mechanical structures, features, and/or other internal parts that must also connect or attach to the housing. These different housing parts and internal parts that must attach to each other are often made from different materials, which can present various challenges in the manufacturing process.
One common mode of attachment is simply to use an adhesive to affix one part to another. The various drawbacks to using adhesives are well-known, and include, for example, relatively lesser limits on bonding strength, the tendency of some adhesives to gradually fail over time, and the possibility that some adhesives do not work well with bonding some materials. This last issue can be particularly problematic where parts made from entirely different materials are to be attached to each other, such as, for example, metal and plastic.
Alternatively, different parts can be welded or otherwise fused to each other as another mode of attachment. In the case of metal parts, however, the high heat associated with a traditional welding process can alter the shape, color and/or texture of the metal parts. Such high heat can also damage or affect other parts that may be in the vicinity of the weld. As such, many types of welds cannot be performed at later stages of an assembly process. Further, the complexity of features or other internal parts is limited to relatively simple components where the fusion welding of metal parts to each other is concerned.
Another common mode of attachment that can be used to attach plastic parts to each other involves ultrasonic welding. Ultrasonic welding of plastic materials is used extensively in many major industries, offers advantages in speed, efficiency and economy, and is often used where parts are too complex or expensive to be molded into a single piece. One big advantage of ultrasonic welding is that heating tends to be localized, such that the ultrasonic welding of plastic parts can take place at various stages of the overall manufacturing process without unduly disturbing nearby parts. Seams and joins of plastic parts that have been ultrasonically welded together can also be quite aesthetically pleasing in comparison with some traditional metallic welds. The ability to ultrasonically weld relatively complex plastic parts together cheaply and efficiently has resulted in the extensive use of plastics in the housings of many electronic devices. For example, various iPod® and iPhone® electronic devices made by Apple Inc. utilize housings having plastic parts that have been ultrasonically welded together.
Unfortunately, the ability to ultrasonically weld plastic parts together has traditionally limited the kinds of materials that can be used where such attachment techniques are to be used. While many thermoplastic parts can be fuse welded together at relatively low temperatures, other materials (e.g., metals) require much higher temperatures for fuse welding. In addition, fuse welding is typically limited to the joining of parts made from the same or similar materials. As such, any desire to substitute metal parts in for plastic parts in a design where welding is the mode of attachment has been traditionally impossible. This serves to limit the abilities of designers with respect to the materials that can be used in a particular design, such as for the housing and internal features or parts of an electronic device having complex internal features. In the event that such a change or adjustment is desired, then the mode of attachment typically must also change from an ultrasonic weld to an adhesive or other type of attachment that is suitable for attaching a plastic part to metal part. For example, where an internal plastic part is to be affixed to an inner surface of a metal housing, then an adhesive or other similar mode of attachment must typically be used.
While many designs and techniques for manufacturing electronic and personal devices have generally worked well in the past, there is always a desire to provide new and improved designs or techniques that can make it easier for a manufacturer or provider to combine parts made of different materials. In particular, the ability to attach plastic parts to metal parts with an approach that is quick, flexible and reliable is desired.